Redefine quoted.Expr.betaReduce #9469
Conversation
nicolasstucki
force-pushed
the
rework-quoted-expr-beta-reduce
branch
from
a24cdc7
to
0c9799e
Compare
nicolasstucki
force-pushed
the
rework-quoted-expr-beta-reduce
branch
from
0c9799e
to
34d2587
Compare
| Expr.betaReduce(fn)(arg) | ||
| def betaReduceImpl[Arg: Type, Result: Type](fn: Expr[Arg=>Result])(arg: Expr[Arg])(using qctx : QuoteContext): Expr[Result] = | ||
| val app = '{$fn($arg)} | ||
| Expr.betaReduce(app).getOrElse(app) |
There was a problem hiding this comment.
If the most common usecase is to do betaReduce(x).getOrElse(x), wouldn't it be nicer to make betaReduce return its input in case it couldn't do any beta-reduction? It would still be possible to explicitly check if it did something by comparing the input and output using eq
There was a problem hiding this comment.
Ok, that might be simpler to use. I will try it out.
nicolasstucki
force-pushed
the
rework-quoted-expr-beta-reduce
branch
from
34d2587
to
89c6ac6
Compare
Redefine `quoted.Expr.betaRduce` to not rely on complex type level computations. Changed the signature as follows ```diff - def betaReduce[F, Args <: Tuple, R, G](f: Expr[F])(using tf: TupledFunction[F, Args => R], tg: TupledFunction[G, TupleOfExpr[Args] => Expr[R]], qctx: QuoteContext): G = ... + def betaReduce[T](expr: Expr[T])(using qctx: QuoteContext): Expr[T] = ... ``` Improvements * Simpler API that covers all kind of functions at once (normal/given/erased) * Better error message for ill-typed `betaRduce` calls * Adds the possiblility of knowing if the beta-reeduction suceeded * Use `transform.BetaReduce` * Improve `transform.BetaReduce` to handle `Inlined` trees and constant argumets * Fixes scala#9466 Drawback * Need for slightly loneger code (previous interface could be implented on top of this one)
nicolasstucki
force-pushed
the
rework-quoted-expr-beta-reduce
branch
from
89c6ac6
to
78f6ee4
Compare
|
test performance please |
|
performance test scheduled: 1 job(s) in queue, 0 running. |
|
Performance test finished successfully: Visit http://dotty-bench.epfl.ch/9469/ to see the changes. Benchmarks is based on merging with master (316d218) |
| @@ -65,7 +69,8 @@ object BetaReduce: | |||
| ref.symbol | |||
| case _ => | |||
| val flags = Synthetic | (param.symbol.flags & Erased) | |||
| val binding = ValDef(newSymbol(ctx.owner, param.name, flags, arg.tpe.widen, coord = arg.span), arg) | |||
| val tpe = if arg.tpe.dealias.isInstanceOf[ConstantType] then arg.tpe.dealias else arg.tpe.widen | |||
| val binding = ValDef(newSymbol(ctx.owner, param.name, flags, tpe, coord = arg.span), arg).withSpan(arg.span) | |||
There was a problem hiding this comment.
It's unclear to me why we cannot just use arg.tpe.widen as the type of the binding?
There was a problem hiding this comment.
It is to allow TermRef to definitions with constant types to be constant folded after this transformation.
| override def transform(tree: Tree)(using Context) = tree.tpe.widenTermRefExpr match | ||
| case ConstantType(const) if isPureExpr(tree) => cpy.Literal(tree)(const) | ||
| case _ => super.transform(tree) | ||
| }.transform(expansion) |
There was a problem hiding this comment.
This is constant folding -- can we reuse the logic in ConstFold?
There was a problem hiding this comment.
It is not exactly constant folding. It is just the propagation of constants. After this ConstFold is used at some point and performs the actual folding.
There was a problem hiding this comment.
What about TreeInfo.constToLiteral?
There was a problem hiding this comment.
It fails. It also looks like overkill.
There was a problem hiding this comment.
OK. Maybe as an optimization for later, beta-reduce & inlining may create new const-folding opportunities.
Co-authored-by: Fengyun Liu <liu@fengy.me>
Redefine
quoted.Expr.betaRduceto not rely on complex type level computations.Changed the signature as follows
Improvements
betaRducecallstransform.BetaReducetransform.BetaReduceto handleInlinedtrees and constant argumetsDrawback